Previous work under this project has: (1) devised a method to study acetylcholine (ACh) turnover by a double-label technique in rats, (2) devised behavioral paradigms to demonstrate central nervous system dysfunction in very early stages of thiamine deficiency, (using a thiamine-deficient diet plus the inhibitors pyrithiamine or oxythiamine), (3) demonstrated decreased ACh synthesis in mild hypoxic hypoxia using method in (1), (4) demonstrated reduced ACh synthesis accompanying central nervous system dysfunction in these very early stages of thiamine deficiency, (5) demonstrated that treatment with cholinergic agents was as effective as thiamine in reversing this central nervous system dysfunction. Future studies will: (a) study the mechanisms of the decrease in ACh synthesis in early thiamine deficiency in more detail, (b) study other vitamin deficiencies such as choline deficiency.